Divers have begun work to repair a leaking subsea gas fuel line at the Middle Ground Shoal oil field in Cook Inlet, field operator Hilcorp Alaska said April 10. Hilcorp discovered the leak in early February and in late March had to shut down the field until the leak is repaired. The company had to wait for sea ice conditions in the inlet to improve before it could safely send down divers to do the repair work.
Diving conditions in the inlet are notoriously difficult because of strong tidal currents and the turbidity of the water.
Hilcorp said that divers have now found the leak point, a 2-inch gash where the pipeline is resting on a boulder embedded in the seafloor. The divers are now preparing for the installation of a temporary clamp over the hole, Hilcorp said.
Following this initial repair, further inspection work will be conducted and a permanent repair of the pipeline will be completed, Hilcorp said. The company said that it will not return the line to service until after the completion of permanent repairs, after the conducting of pressure testing of the line, and after approval of the restart by government regulators.
Oil leak investigationDivers have also been investigating an oil leak at the Anna platform on the west side of the inlet. On April 1 Hilcorp shut down oil production from the platform after an oil sheen and bubbles were observed near one of the platform legs, following a sudden shuddering of the platform. With a leak in the subsea pipeline between the Bruce and the Anna platforms being the suspected culprit, Hilcorp shut in the line, replacing the oil in the line with seawater.
However, divers have now inspected the pipeline and determined that the line is intact, Hilcorp says. Moreover, a successful hydrostatic pressure test of the line, observed by officials from state and federal agencies, demonstrated that the line is in good working order, the company says. The pipeline was tested to 125 percent of its maximum operating pressure for eight hours.
And, so, with the cause of the oil leak yet to be determined, an investigation of the incident continues.
Following the gas leak at the Middle Ground shoal field, Hilcorp began a review of all of its pipeline assets in the Cook Inlet. Subsequently the company found a metering discrepancy between the volume of gas delivered to a gas pipeline from the Steelhead platform and the gas delivered from that pipeline at the point where the pipeline connects to an onshore gas processing facility. The company conducted several overflights of the pipeline route but could not find any indications of a subsea gas leak. However, as a precaution, the company has closed down the pipeline and filled the line with seawater, pending a further investigation of the metering discrepancy.
Investment in the stateSince entering the Cook Inlet oil and gas industry in 2011 Hilcorp has invested several hundred million dollars in the region and, in the process, has upped oil production from the Cook Inlet basin and has been the key player in averting a pending utility gas supply crisis in Southcentral Alaska. However, in its operations both in Cook Inlet and on the North Slope, the company has on several occasions run afoul of Alaska oil and gas safety laws. The Alaska Oil and Gas Conservation Commission has fined the company several times for regulatory violations. In response, Hilcorp has expressed its desire to work openly to ensure safe and responsible operations.
During an Alaska House Resources Committee meeting on April 5 Kristin Ryan, director of the Division of Spill Prevention and Response at the Alaska Department of Environmental Conservation, commented that Hilcorp had been working cooperatively with DEC in responding to the leak in the Middle Ground Shoal gas line.
“To their credit, they have done everything we’ve asked them to do, even although we don’t have specific regulations requiring this activity,” Ryan said.
Ryan said that the biggest concern with the gas leak is the potential for methane gas to displace oxygen in the water column, a phenomenon that could impact the ability of fish to breath. However, tests of water samples collected by Hilcorp from the area of the leak had thus far proved inconclusive, she said. The state’s interest in natural gas safety has tended to revolve around the potential for a gas explosion - the state has not in the past seen any particular environmental concern with natural gas pipelines, she said.
Aging assetsHilcorp’s business model particularly focuses on bringing new life to aging oil and gas assets. And in Cook Inlet many of the company’s assets, including several subsea oil and gas pipelines, date back to the 1960s. The age of the facilities and the sudden appearance of three leakage incidents are raising concerns about the overall condition of the subsea pipelines.
The Pipelines and Hazardous Materials Safety Administration, the federal agency that oversees oil and gas pipeline safety, now wants Hilcorp to inspect the subsea oil line that delivers Middle Ground Shoal oil to shore. The oil line and the gas line run in close proximity to each other, are both 8 inches in diameter and are of similar construction.
“We need to take a look at the infrastructure in the Cook Inlet and we recognize that it’s been since 2000 since there’s been a real assessment of what’s out there, who owns it, what are they doing with it,” Ryan told House Resources. “We do have our standards for pipelines that are the same if it’s a new pipeline or an old pipeline, and I can say that Hilcorp has been in compliance with our standards for their infrastructure.”
Hilcorp runs pigs through its subsea lines and conducts sonar scans that enable the company to determine if the pipelines are adequately supported on the seafloor, Ryan said.